(1) Field of the Invention
The present invention relates to a method of producing color filters. More particularly, the present invention relates to a method of producing color filters having an improved filter base.
(2) Description of the Prior Art
Color filters comprising an organic material have been used for image pickup devices such as solid state color image pickup devices and single color image pickup tubes. These color filters have heretofore been prepared by adding ammonium dichromate to an organic polymeric material such as polyvinyl alcohol (ordinarily referred to as "PVA"), gelatin or casein to form a filter base having a light sensitivity, subjecting the filter base to imagewise exposure through a mask pattern and to development and drying the filter base. According to this method, warm water or the like is used at the development step, and after rinsing, the filter base is dried under rotation by using a spinner. The filter base absorbs a large quantity of water at the development step to increase the volume thereof by swelling. Ordinarily, the above-mentioned rotational drying is adopted for removing water from the filter base after the development step. According to this method, however, when water is scattered at a high speed, the filter base is deformed, and the original shape is not restored by drying. This results in distortion of the pattern and a precise pattern cannot be obtained.
The following prior art references are cited to show color filters:
U.S. Pat. No. 4,081,277
U.S. Pat. No. 3,623,794
"Integral Color Filter Arrays for Solid State Imagers", DIGEST OF INTERNATIONAL ELECTRON DEVICE METTING, December 1970, page 460